Cooling the World Cup: USA vs Qatar

Two approaches to conditioning large football stadiums in warm climates.

Only three U.S. World Cup venues can genuinely be described as actively cooled match stadiums: Atlanta, Dallas and Houston. The key point is not concourse air-conditioning, but the ability—when the retractable roof is closed—to condition the spectator bowl and pitch as one large indoor volume. 

This is effective, but not subtle. The U.S. strategy is to enclose first and cool second. Qatar 2022 used a different logic: architectural form, air movement and local supply to create cooled microclimates around spectators and the pitch. The real comparison is therefore not whether cooling works, but how efficiently, evenly and robustly it delivers comfort, using the least possible energy. 

Is active cooling necessary in football stadiums? 

In June and July, outdoor temperatures in Atlanta, north Texas and Houston can exceed 35°C / 95°F. Atlanta and Dallas have similar absolute humidity, around 17 g/m³, while Houston is closer to 20 g/m³, meaning roughly 20% more moisture in the air. Houston is therefore the most latent-load driven case: the plant must remove water vapour as well as heat. 

For players, high wet-bulb conditions reduce evaporative heat loss, increase cardiovascular strain and can reduce high-intensity running. For spectators, long dwell times, queuing, alcohol consumption and limited personal control turn heat into a crowd-safety issue. Cooling is therefore part of the event strategy, not a luxury. The weakness is that it depends on treating each stadium as a sealed building: roof open, doors open, uncontrolled solar gains or leakage at the retractable roof perimeter all make the cooling task less elegant and more energy intensive. 

Atlanta Stadium: integrated, but still a huge, conditioned volume 

Atlanta is the most integrated of the three. Its retractable roof closes the bowl, and the stadium combines daylighting, automated controls, LED lighting and a wider sustainability narrative. It is closest to a whole-building proposition rather than simply a stadium with a very large chiller plant. 

The cooling principle is still conventional: reduce air exchange, enclose the volume, and condition it with high-capacity HVAC. This should give stable operative temperatures once the roof is closed. The limitation is the envelope: a large roof aperture, translucent roof elements and a very high internal volume all carry thermal penalties. It may be efficient by U.S. mega-venue standards, but that is a low bar compared with reducing the conditioned volume or supplying comfort locally. 

Dallas Stadium: effective comfort, blunt energy logic 

Dallas is the clearest expression of the U.S. model: close the roof and operate the stadium as a giant air-conditioned arena. Reported closed-roof conditions are around 22–24°C / 72–75°F even when outdoor temperatures are close to 35°C / 95°F and perceived outdoor conditions approach 41°C / 106°F. Technically, that is a successful comfort outcome.  The cost is energy intensity. Published estimates put Dallas close to 100,000 kWh per match for air-conditioning. In U.S. energy terms, that is about 341 million BTU of electrical input per match before considering plant efficiency and distribution losses. Even allowing for uncertainty, the order of magnitude is telling: comfort is delivered primarily by plant capacity, not by climatic intelligence. The system works, but success is bought mechanically. 

Houston Stadium: the clearest envelope warning 

Houston is the hardest case because heat and humidity combine. With the roof closed, the stadium can act as a conditioned bowl and protect spectators from direct sun and rain. But it also shows why ‘retractable roof’ and ‘thermal envelope’ are not the same thing. The stadium performs well only when the roof and major openings are treated as a serious thermal boundary.  When the roof is open, solar exposure is uneven: south and west areas are generally more protected, while north and east areas are more exposed. This matters because mean radiant temperature can rise even if the air temperature is acceptable. In those conditions, internal shading and strict roof/opening control become part of the cooling strategy, not operational footnotes. Air leakage, roof perimeter gaps, large volumes and solar penetration all reduce the effectiveness of mechanical cooling.

Qatar 2022: targeted microclimate rather than cooled void 

Qatar’s strategy was fundamentally different in the 2022 world cup. It did not attempt to cool an entire stadium void. The principle was spot cooling: supply cool air where people and players actually are, through grilles in the stands and larger pitch-side nozzles. Stadium form, insulation, air recirculation, filtration, wind-tunnel testing and CFD were used to contain a cooled microclimate within a semi-open condition. 

This is a more interesting comfort strategy because it starts from the occupied zone: the spectator’s ankles, the occupied tier, the player and the pitch boundary layer. It also recognises that comfort depends on radiant temperature and air movement, not only dry-bulb temperature. The U.S. approach is simpler and probably more robust operationally: close the roof, set a temperature, run the plant. But it cools a very large volume whether or not each cubic metre contributes to comfort. Qatar’s approach was not free of energy or carbon questions, but conceptually its efficiency argument is stronger because comfort was targeted rather than volume-wide. 

What monitored data is available? 

The evidence base is thinner than it should be. For the U.S. venues, the best public energy figures are estimates rather than confirmed BMS or utility-meter data: approximately 99,925 kWh per match for Dallas, 97,344 kWh for Houston and 96,020 kWh for Atlanta. Dallas also has a reported internal range of 22–24°C / 72–75°F, but without relative humidity, air speed, radiant temperature or sensor locations, this is not a full comfort dataset. 

For Qatar, the public evidence is technically richer—CFD, wind-tunnel work, targeted supply, air recirculation and reported target conditions around 18–24°C / 64–75°F—but still not equivalent to transparent post-occupancy monitoring. One CFD-based study reported acceptable comfort under external conditions up to 48°C / 118°F and 70% relative humidity, with many zones maintaining thermal neutrality even when cooling load was reduced by about 50%. That supports the design logic, but it remains modelled evidence, not match monitoring. 

A rigorous comparison—kWh per spectator-hour, kWh per comfort-hour, or WBGT reduction per kWh—is therefore not possible from public sources. The available evidence suggests that U.S. closed-roof cooling works, while Qatar’s strategy is conceptually more energy efficient. But neither case has yet published enough monitored data to prove performance transparently. 

Lessons learned 

First, enclosure works only if it is treated seriously. A retractable roof becomes a thermal envelope only when airtightness, solar control, perimeter detailing and operational discipline are adequate. 

Second, comfort must be measured at the occupant, not the thermostat. Air temperature alone is insufficient; radiant temperature, humidity, air speed, stratification and crowd density all matter. 

Third, energy efficiency depends on reducing load before increasing plant size. Qatar’s hierarchy—shade, shape, contain, supply locally, recirculate, then cool—is better environmental design. The U.S. model starts further downstream: close the lid and cool the room. 

The conclusion is simple: Atlanta, Dallas and Houston can host safe, comfortable matches, but they should not be mistaken for low-energy precedents. The best cooling strategy is not a bigger chiller. It is a better solar control, better scheduling (i.e. hosting games at cooler hours of the day) and a better envelope.

Classroom overheating in Barcelona: HVAC simulation study

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Introduction: why classroom overheating matters

As climate change intensifies summer heatwaves, preventing classroom overheating has become a critical design challenge for educational buildings in Mediterranean cities such as Barcelona. Schools must provide healthy, comfortable indoor conditions while also reducing energy consumption and operational complexity.

This article presents a thermodynamic building simulation study assessing overheating risk in two primary-school classrooms in Barcelona. The analysis uses DesignBuilder with the EnergyPlus calculation engine to evaluate whether a centralised 100% outdoor air HVAC system can maintain thermal comfort during school hours from May to September.

The study is relevant for architects, engineers, school operators and public authorities seeking evidence-based strategies for thermal comfort in schools, especially where cooling is delivered through a central air-handling unit rather than room-by-room terminal units.

* Schools shut in Spain from the end of June until September. However, for the simulations, July and August were included in the simulations, to have results under more challenging climate conditions. This was also done as the climate file is based on historical data. Currently, weather conditions that typically occurred in July now often occur in May.

Thermal comfort criteria

Thermal comfort was assessed using operative temperature thresholds during school hours only. The comfort band was defined as 22°C to 27°C, with indoor relative humidity targets between 30% and 60% at 26°C. Conditions below 22°C were classified as too cold, while conditions above 27°C were classified as too hot.

Using operative temperature rather than air temperature alone provides a more representative assessment of how occupants experience the room, because it accounts for both air temperature and radiant temperature from surrounding surfaces.

Key results: overheating and overcooling risk

External Climate Overview (08:00–18:00, Mon–Fri)

The analysis shows that the central HVAC system generally maintains classroom comfort for most teaching hours. However, the results also demonstrate that orientation, solar gains and supply-air control are decisive factors in determining real comfort performance.

The east-facing classroom experiences the highest overheating risk, particularly in July and September, because morning solar gains coincide with early occupancy and rising outdoor temperatures. In July, the east classroom exceeds 27°C during approximately 7% of teaching hours despite the supply air being delivered at 14°C.

The west-facing classroom performs slightly better in terms of overheating, with only a small proportion of hours above 27°C in September. However, it is more exposed to overcooling in the morning during shoulder months, because delayed afternoon solar exposure does not compensate for early cool supply air.

This finding illustrates a common HVAC design challenge in schools: a single central control strategy can perform adequately on average while still creating different comfort outcomes across zones with different orientations.

Passivhaus Homes in Tordera: BYKO completes the Guifré el Pilós development certified by Praxis

In Tordera (Barcelona), BYKO has completed the Guifré el Pilós development: a set of three terraced homes designed and built to meet the Passivhaus – Low Energy Building standard, with certification carried out by Praxis Resilient Buildings. The project was developed in collaboration with La Llotja Arquitectes and is located in Tordera, province of Barcelona, Catalonia, Spain.

Architecture

Each home is arranged over two floors with a treated floor area close to 100 m² and a highly functional layout: open‑plan kitchen-living‑dining room, and a full bathroom on the ground floor; and on the first floor: two single bedrooms, a master bedroom with en‑suite, an additional bathroom, a utility/plant room and a study area. Private front and rear patios complete the programme.

Construction system, structure and 2D prefabrication

The construction system uses 2D industrialised lightweight timber‑frame modules for walls and roof, reducing on‑site time and ensuring precision—key to achieving Passivhaus‑level of air‑tightness and thermal‑bridge control. Modules were delivered with the air‑tight layer (FINSA Superpan timber particle board) and external thermal insulation (pre‑render) already installed. Windows are PVC with triple low‑e, solar‑control glazing, and motorised shutters for summer shading.

Building services, ventilation and indoor air quality

• Balanced mechanical ventilation with heat and moisture recovery (Zehnder Climos 200) for continuous fresh air, minimal thermal loss and effective particle filtration.
• Space conditioning via air‑to‑air heat pump with ducted indoor units, sized for the building’s low heating and cooling loads.
• Domestic hot water via an air-to-water heat pump hot water unit with a 190‑L tank; seasonal efficiency for DHW of SCOP = 3.52.
• Loxone monitoring and controls (ventilation, HVAC, DHW and general electricity) for optimisation and maintenance.
• Optional rooftop PV to further improve the energy balance.

Passive design, air‑tightness and thermal bridges

As part of the Passivhaus certification, Praxis verified air‑tightness (n₅₀) via blower‑door testing, the elimination of thermal bridges at envelope junctions and openings, active solar protection with motorised shutters, and proper commissioning of the MVHR system. These measures cut heating and cooling demand and deliver 24/7 comfort with very low energy use.

360º comfort

• Homogeneous indoor temperatures without drafts or noticeable stratification.
• Consistently healthy indoor air quality thanks to MVHR with filtration (CO₂ and VOCs kept in check).
• Low noise levels due to the high‑performance envelope and windows.

Voices from the project

“With Guifré el Pilós we reaffirm our commitment to ultra‑low‑energy, high‑comfort homes, bringing the Passivhaus standard to families who value quality, health and efficiency,” says Ismael Fernández, developer and builder at BYKO.

“Passivhaus certification rigorously validates real‑world building performance. At Guifré el Pilós, we paid careful attention to air‑tightness, thermal‑bridge control, high‑efficiency ventilation and summer performance, to ensure year‑round comfort,” says Oliver Style, Passivhaus certifier at Praxis Resilient Buildings.